Variable time characteristic relay



March 22, 1938. w. v. JOHNSON 2,112,098

VARIABLE TIME CHARACTERISTIC RELAY Filed June 1'7, 1936 2 Sheets-Sheet l INVENTOR 2 2/1027 lu /mam.

WITNESSES: had/M mh' 1938 w. v. JOHNSON 2,11 ,0

VARIABLE TIME GHARACTERISTIC RELAY Filed June 17, 1936 2 Sheets-Sheei 2 WITNESSES: INVENTOR WWW iV/zon XJo/Yms 072.

I BY

ATT EY Patented Mar. 22, 1938 UNITED STATES PATENT .orrlca to Westinghouse Electric & Manui' acturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 17, 1936, Serial Non 85,634

9 Claims. (Cl. 175-294) My invention relates to protective relays for electrical circuits and apparatus and particularly to such relays which operate with a variable time delay dependent upon the magnitude of an electrical condition. Although not limited thereto, my invention is particularly applicable to overcurrent and distance relays for general protective purposes in alternating current systems of transmission and distribution.

Various relays have heretofore been proposed for such applications, which involve a fault responsive element such as an induction disc motor, and a constant speed element, such as a clock mechanism or synchronous .motor, arranged to control'the relative movement of a pair of coopcrating contacts. The induction disc element may be spring biased to produce a variable deilection or may operate at variable speed ag- -st the drag of a permanent magneh and the mechanical arrangement for operating contacts may assume any of a number of terms, depot. ent upon the time characteristics 1' Although many such arrangements pr theoretical characteristics of highly form, it is usually impossible to characteristics in practice because 0 limitations of the arrangement. culty is that the contact movem minimum time operation is excess 3 either a high minimum operating t curacy of timing the shorter i cause of mechanical oscillations. ciency precludes use of the relay o": higi i s applications and imposes undesiraeie restr" on its use for other purposes.

It is an object of my invention prowl-1e a novelvarlabletime characteristic relay which will follow any desired time characteristic of a line variable with uniform accuracy at all points and 'will provide a substantially instantaneous minimum operating time.

Other objectsof my invention will become evi dent from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

Figure 1 is a plan view of an overcurrent relay embodying my invention;

Fig. 2 is a sectional view taken on the line 11-11 of Fig. 1; I Fig. 3 is a sectional view taken on the line III-411 of Fig. 2;

Fig. 4 is anelevational view" of a preferred form of g rrent transformer to be used in the practice of y invention.

Fig. 5 is a diagrammatic view of an over-curbodying my invention;

Fig. l is a sectional view taken on the line ViIVlI of Fig. 6;

Fig. 3 is a sectional view taken on the line VHl-VIII of Fig. '2;

Fig. 9 is a fragmentary sectional view taken on the line lX-Di of Fig.8, showing a detail of the timing motor;

Fig. 19 is a diagrammatic view of an impedance protective system embodying the relay of Fig. 6;

Fig. ll is a plan View of an. improved magnetic circuit for the relay of Figs. 1 to '4; and

l2is a view in end elevation of the magnetic shown in Fig. ll.

. r Referring "o l, 2 and which show an 261 adaptation of the invention for over-current pro tection, a base plate l, of suitable insulating ma terial, is secured to a magnetic structure J, by

of suitable halts 3 to constitute an enclosure therewith for the operating oi relay. The W netic structure 2 comprises an outer shell poi ion 1 and a core portion us ranged to constitute iron-clad. type magnetic for the relay ce l. A)

"the core portion is drilled at 6 to form re- I cess, in which a shaft 3 is rotatahly mounted hy eams of suitable hearings ii. The shaft car-= ries a yoke W, splinecl or otherwise suitably se cured thereto, to rotate therewith, a circular 35 plate it is secured to the yoke l l) by means ct a thumb hut and a pin it. A movable magnetic element for cooperation with the magnetic struc= ture 2, preferably in theiorin of a cam M, is secured to the circular plate M by any suitable 40 means. so as to form a variable air gap with the shell portion A helical spring is mounted within the recess 6 arranged to bias the shaft 8 to arr-initial position against an adjustable viously, various equivalent adjustments known in the art may be substituted for the specific structure shown. 55

A movable magnetic operating member is mounted in the air gap between the magnetic cam I4 and the shell portion 4 of the magnetic structure 2. The operating member may assume 5 any of a number of forms, but preferably comprises a pivoted armature 22 of magnetic materiaLmountedsoastorotateinaDIime through the axis of the shaft 8. The armature 22 is provided with a movable contact 23 which cooperates with suitable stationary contacts 24. Conducting terminals 25 are mounted on the base plate i and may be connected with the stationary contacts 24' and moving contact 23 in well known manner. The form of contact structure used, of course, is susceptible to many variations familiar to those skilled in the art.

A suitable biasing or restraining element for the magnetic armature 22 is provided for maintaining the latter in an initial position, in which the back contact circuit of the relay is completed, and the front contact circuit is open. The restraining element preferably comprises a permanent magnet 26 secured to a bracket 264 by means of a bolt 21. The bracket 2 may be secured to theshellportionofthemagneticstructure2by means of suitable machine screws 210. A permanent magnet is preferred for this purpose for the reason that its biasing or restraining force substantially disappears upon the slightest movement of the armature, so that the latter movement is fast and posiflve.

The magnetic cam II is provided with a graduated periphery, preferably of generally spiral contour,so astoprovideavariableairgapin the magnetic circuit comprising the shell portion 4, the core portion 5 and the cam ll. Upon rotation of the cam ll, the variable air gap varies the reluctance of the magnetic circuit, and thereby varies the attractive force acting upon the armature 22 and tending to move the latter from its initial position to its operating position.

The lower portion of the magnetic structure 2 isrecessedtoprovideachamberforachrtchassunbly 28. The clutch assembly 22 is preferably enclosed. by means of a magnetic cover plate 2!, whichalsoservesasthebaseplateofanadjustable speed motor ll. The cover plate 22 is secured in place over the clutch w- 20 by any suitable means, such as bolts ii. The clutch bly 2. comprises a coil 32, mounted within the enclosure, in position to surrolmd a magnetic driving plate 33, loouly splined to the shaft 2, andadrlvenplate ,whichisrigidlysecmedto the shaft of the motor 3.. ans driving puts a is provided with a suitable facing ii, of resilient material, which extends outward slightly from the face thereof and is compressed flush with the latter upon a clutching operation of the bly. Acopperlagloopli issetinthefacelof during operation of the clutch, to thereby prevent release of the clutch at thesero points of magnetization. The clutch 2. permits rapid return of the cam ll to its initial position upon '55 de-tion of the relay, to thereby prepare the driven plate II, to provide quadrature iiux' auaoos ent invention, a detailed description thereof is omitted It will be understood, however, that the motor 3| when from a suitable alternating-cm'rent source, operates at a constant adjust ble speed in the-direction corresponding to the clockwise direction of Pig. 1.

Fig.4showsanadjustableauxiliarytransformer II, of a preferred type for use in the overvcurrent protective circuit which will be hereinafter described in connection with Fig. 5a. The auxiliary transformer 31 comprises an outer shell of magnetic material 22, preferably laminated in well known manner, and to receive a sliding core 22. The slidlns core 30 is mounted on an adjusting bolt 4. for movement centrally with reference to the outer shell 38. A stationary primary winding Ii and a stationary secondary winding 42 are mounted within the shell portion 38 in podtion to surround the core 39. Upon adjustment of the position of the core ll by means of the adjusting bolt II, the flux distribution within the magnetic core is changed so that the mutual reactance of the auxiliary transformer may be increased while the transformer leakage reactance is decreased, or vice versa. In this way the secondary current of the transformer, for constant primary current and a load of constant impedance and impedance phase angle, may be varied through a considerable range of values. I have found in practice that secondary voltage variationsottheorderofiitolcanbesecured with all intermediate graduatimaby means of thisdevice.

Fig. 5 shows the electric circuits, associated with therelayshowninl'lgs. 1,2and 3, forusein the protection of an alternating-current power circuit against over-cm'rents. In l ig. 5, the alternating-current power circuit, which may be a ton or distribution feeder, is denoted by the reference numeral 45, and a circuit breaker 46, of any suitable type is provided for interruptingthecurrentiiowintheeventofa'fault. The circuit breaker 48 is provided with the usual trip coil ll,whichisconncctedincircult withasuitable source of power, such as a battery I. and the front contacts of the relay, shown diagrammaticallyat tbeleftofthengure.

A line current transformer 62 is provided and connected with its secondary winding in series with an initiating element N, the coil 1 of the relay and the primary winding of the saturable transformer I. The initiating element N is provided with back contact members. II, which are connected in parallel with the secondary winding of a saturable transformer I, the energised windingof motorflandthewindingfloftherelay clutch. With this arrangement, the contacts I normally short circuit the secondary circuit of the saturable transformer II, and prevent the circulation of current thro s the energizing windingofthemotoril andtheciutchcoilfl.

The initiating element ll, although shown separatefromtherelaypropenmaybeapartof the-relay, aswill be hereinafter explained in connection with Figs. 6 to 10. --The initiating elementiiissdjustedordesignedtorespondto the minimum valueof fault current of the power circuit .atwhichanoperationof the circuit breakerllisrequired. Themsgneticcamllis positioned by means of its adjustable stop (siowninl iglltoapositioninwhichtheair gap between the cam II and the armature 22 isofsuchmagnitudeastorequirethemaximum over-current value of the eurrentin the power eircuitlltoexistforoperationofthe-armature and the initiating element 50 opens to insert the energizing winding of the motor 30 and the winding 32 of the relay clutch in series with the secondary winding of the saturable current transformer 65. A force dependent in magnitude upon the line current is, accordingly, exerted on the armature 22, because of the magnetic action of the relay winding 1 in the magnetic circuit 01 the relay proper. If the line current exceeds the setting corresponding to the adjustment of the cam H, the armature 22 moves to its operating position instantaneously, thereby establishing an energizing circuit for the trip coil M, and causing the circuit breaker 46 to open.

If the value of over-current in the line circuit 45 does not exceed the instantaneous setting of the cam M, the armature 22 does not immediately move to its operating position, and the motor 3!] acts through the clutch 28 to drive the cam it in the proper direction to reduce the air gap between the cam I4 and the armature 22 (clockwise in Fig. 1). As the cam i4 rotates, the reluctance of the relay magnetic c t gradually diminishes, and the force ten the armature 22 progressively int; that the current in line 65 re When the operating force producer. by relay coil 7 and its associated magnetic ture reaches a value slightly greater than 1 restraining force exerted by the permanent magnet 26, the s operated aosition, thereby tripp" orealzer GS the manner described a. 3'9

It willbe apparent that the terlstics cf the relay i of the cam It, the s the initial position i any or all oi these i s, y desired cvei c rent characteristic, both as to ti yalues,'can be @ne dies. a of the earn it is e. spiral of such i as to dnce straight line over-current c a ct such as described in the Unite es of S. L. Goldsborough, No. 1,973,063, issue: tember Ill, 1934, and assigned to the Viewhouse Electric 8: Manufacturing @ompany, and in the United States patent of R. M. Smith, No. 2,071,857, issued February 23, 1937, and assigned i the 53E], P

to the Westinghouse Electric '81 Manufacturing Company.

In some applications it is desirable to provide adjustment of the over-current setting in infinitely fine gradations over a wide range of current values. Such adjustment may be eflected by utilizing the adjustable transformer 31, shown in Fig. 4, in connection with a suitable modificationcf the energizing circuits of Fig. 5. Such a modification is shown in Fig. 5a. It is believed. that the operation of this arrangement will be obvious from that described above in connection with Figs. 1 to 5.

Referring to Figs. 6 to B, an application of the invention as an impedance relay for general alte'rnating-current application is shown therein.

In this figure, the base plate I, magnetic structure 2, relay coil 1, shaft 8 and armature 22 are similar to the corresponding elements of Figs. 1 to 3 and are designated by the same reference numerals. In place-of the adjustable speed po= larizing vibrator motor 30 oi! Figs. 1 to 3, however, a synchronous motor 55 is shown as a driving element for the shaft 8 and magnetic cam I4. It will be obvious that the vibrator motor 30 of Figs. 1 to 3 and the synchronous motor 55 of Fig. 6 serve the same purpose of producing timed movement of the cam l4 and may he used interchangeably, or may be replaced by functionally equivalent apparatus of entirely different form.

The synchronous motor is preferably of the type in which the armature moves axially, when the coil is deenergized, to a position such that a pinion carried onthe armatureshaft is disengaged from a gear wheel associated therewith during operation of the motor. This feature is shown in Fig. 9.-

Referring to Figs. 7 and 8, the synchronous motor 55 is connected by means of a gear train 5? to the shaft 8 for driving the magnetic cam it. As the axial movement of the armature of the synchronous motor 55 serves to disconnect the cam M from the motor armature, the cam it may be restored to its initial position upon deenergization of the synchronous. motor 5, without the use oi an electromagnetic clutch, such as shown in Figs. 1 to 3.

In place of the helical spring 95 of Figs. 1 to a flat spiral spring is provided for rotating the cam i l to initial position. An adjustable stop, to that shown at it in Fig. i, may I; em, but simplicity has been omitted y shown in Figs. 6 to 8,

strained by h serves a purpose si shown in i ting element Sta, cl

the armature number of s able may d s seed the ma- "1e various new.

will u derstooi that the initiating element We serve'" the same purpose in initiating cper ation of relay, as the separate initiating ele ment 5i) of Fi 5.

Fig. l shows the electric circuits associated with the impedance relay of Figs. 6 to 8. In this figure, the power circuit 45, circuit breaker it, trip coil 411, battery 48, line current transformer 49) and saturable transformer 65 are similar to corresponding elements of Fig. and are designated by the same reference numerals. In addition to the line current transformer 49, a line potential transformer till is provided for obtaining the voltage variable necessary for application to the relay restraining magnets. The operation of the impedance relay circuits shown in Fig. 10 will be obvious from the operation described above in connection with the over-current relay shown in Figs. 1 to 5. v

Referring to Figs. 11 and 12, an improved magnetic structure for the relay of Figs. 1 to 4 is shown therein. In place of the iron shell of Figs. 1 to 4, an outer magnetic circuit 10 of substantially rectangular form, having an inwardly projecting pole Ii, is provided. The outer magnetic circuit III is preferably composed of flat laminations of silicon steel, and a similarly laminated cam 12, having thesame function as the cam ll of Fig. 1 is rotatably mounted within the magnetic circuit 10, in cooperative relationship with the pole I l.

A relay armature 13, preferably of silicon steel having channel form, is pivoted by any suitable means, indicated diagrammatically at ll, in a position to be attracted by the cam 12 when the latter is sufiiciently energized. Magnetic energization is supplied by a coil I5, mounted on the pole II to serve the same purpose as the coil 1 of Fig. 2. In place of the permanent magnet restraining element 26 of Figs. 1 to 4,

a small magnetically saturable stud I6 is provided in a position to engage the magnetic circuit I0 and the armature I3 when the latter is in its normal position. The stud 16 may be secured to either the armature 13 or the magnetic circuit 10 and preferably is made of a ferromagnetic nickel-iron alloy.

At low values of magnetomotive force acting in the relay magnetic circuit, the stud 16 carries a relatively large proportion of the flux acting upon the armature l3, and accordingly tends to'restrain the latter. At much larger values of magnetomotive force, the flux carried by the stud 16 is limited because of magnetic saturation, and the operating force acting on the armature 23 exceeds the restraining force, causing the armsture 13 to move to its tripping position. The circuits used are the same as those of Fig. 5, and the operation, except as explained above, is identical with that of the relay shown in Figs. 1 to 5.

The characteristics of the impedance relay of Figs. 6 to 10 may be modified in various ways, as mentioned in connection with the over-current form of the invention. By suitably designing the contour of the cam l4, straight line impedancetime curves of uniform slope may be secured. or various stepped characteristics consisting of sloping portions and portions parallel to or perpendicular to the time axis may be secured. Obviously, other desirable impedance-time characteristics may be secured. Reactance or other distance characteristics may be secured by modifying the phase relationship of current and voltage energization in well known manner.

I do not intend that the present invention shall be restricted to the specific structural details, arrangement of parts, or circuit connections herein set forth as various modifications thereof may be effected without departing from the spirit and scope of my invention. I desire, therefore, that only such limitations shall be imposed as are indicated in the appended claims.

I claim as my invention:

1. In a. relay responsive to an over-current condition of an electric circuit, a magnetic operating member biased to an initial position and movable to an operating position, electromagnetic operating means for said member forming a magnetic circuit therewith, said electromagnetic op erating means comprising a core portion energized in accordance with a current condition of said electric circuit and a rotatable portion included in said magnetic circuit, said rotatable portion having a graduated periphery arranged to vary the reluctance of said magnetic circuit, andtiming means for controlling rotation of said rotatable portion. I

2. In a relay responsive to an overcurrent condition of an electric circuit, a magnetic operating member movable from an initial position to an operating position, electromagnetic operating means for said member forminga magnetic circuit therewith and tending to move said member to said operating position, said electromagnetic operating means-comprising a core portion energized in accordance with a current condition of said electric circuit and a rotatable portion of variable radius included in said magnetic circuit and arranged to vary the reluctance thereof, a permanent magnetic restraining element tending to hold said magnetic operating member in said initial position against the force exerted by said electromagnetic means, and a timing motor for rotating said rotatable portion.

3. In a relay responsive to an abnormal condition of an electric circuit, a plurality of magnetic operating members located at spaced positions, energizing means for said operating members including winding means energized from said electric circuit and including magnetic structure defining an individual air gap region for each of said operating members, said magnetic structure being designed to provide a variable characteristic for each of said operating members dependent upon the reluctance of the corresponding air gap region, a magnetic element having a graduated periphery, and means for moving said magnetic element through said air gap regions to thereby progressively vary the operating characteristics of said operating members.

4. In a relay responsive to an abnormal condition of an electric circuit, a plurality of magnetic operating members located at spaced positions substantially equidistant from a predetermined axis, energizing means for said operating members including winding means energized from said electric circuit and including magnetic structure defining an individual air gap regionfor each of said operating members, said magnetic structure being designed to provide a -variable operating characteristic for each of said operating members dependent upon the reluctance of the corresponding air gap region, a magnetic cam element mounted for rotation on said axis to traverse said air gap regions, said cam element having a graduated periphery to progressively vary the operating characteristics of said operating members, and a motive device for rotating said cam element.

5. In a relay responsive to an abnormal condi-' tion of an electric circuit, a movable magnetic circuit element having a graduated periphery designed to provide non-uniform magnetic reluctance in a direction perpendicular to a predetermined path at a plurality of points on said path, a plurality oi magnetic operating members located at spaced points adjacent said path and movable in response to forces perpendicular to said path, a common magnetizing means for producing a magnetomotive force dependent upon a condition derived from said electric circuit and acting in a magnetic circuit which includes said magnetic operating members in parallel relationship and which includes said magnetic circuit element, and motive means for moving said magnetic circuit element.

6. In a relay responsive to an abnormal condisized in accordance with a current condition of tion 01' an electric circuit, a magnetic circuit element rotatable about an axis and having a graduated periphery designed to provide non-uniform magnetic reluctance in radial direction at a plurality of points on a circular path concentric with said axis, a plurality of magnetic operating members located at spaced points adjacent said circular path and movable in response to forces normal to said path, a common magnetizing means for producing a magnetomotive force dependent upon a condition derived from said electric circuit and acting in a magnetic circuit which includes said magnetic operating members in parallel'relationship and which includes said magnetic circuit element, and a motor for rotating said magnetic circuit element.

7. In a relay responsive to an ohmic characteristic of an electric circuit, a pluraiity of magnetic operating members located at spaced positions, electromagnetic means energized in accordance with a current condition of said circuit ior exerting operating forces on said members, electromagnetic means energized in accordance with a voltage condition of 'said circuit for exerting restraining forces on said members, one of said electromagnetic means including magnetic structure defining an individual air gap region for each of said operating members, said magnetic structure being designed to provide a variable characteristic for each of said operating members dependent upon the reluctance of the corresponding air gap region, a magnetic element having a graduated periphery, and means for moving said magnetic element through said air gap regions to thereby progressively vary the operating charac teristics of said operating members.

8. In a relay responsive to an ohmic charac teristic of an electric circuit, a. plurality of magnetic operating members located at spaced positions, a common electromagnetic means enersaid circuit for exerting operating forces onsaid members, individual electromagnetic means energized in accordance with voltage conditions of said circuit for exerting restraining forces on said members, said common electromagnetic means including magnetic structure defining an individual air gap region for each of said operating members, said magnetic structure being designed to provide a variable characteristic for each of said operating members dependent upon the reiuctance of the corresponding air region, a magnetic element having a graduated periphery, and means for moving said magnetic element through said air gap regions to thereby progressively vary the operating characteristics of said operating members.

9. In a relay responsive to an ohmic characteristic of an electric circuit, a plurality of magnetic operating members located at spaced positions substantially equidistant from a predetermined axis, electromagnetic means energized in accordance with a current condition of said circuit for exerting operating forces on said members, electromagnetic means energized in accordance with a voltage condition of said circuit for exerting restraining forces on said members, said first-mentioned electromagnetic means including magnetic structure defining an individual air gap region for each of said operating memhere, said magnetic structure being designed so that the magnetic reluctance of said air gap regions normally prevents operation of the corresponding operating member, a magnetic cam element mounted for rotation on said aids to traverse said air gap regions, said cam element having a graduated periphery to progressively reduce the reluctance of said air gaps and a motive device for rotating said cam element.

WEL'I'ON V. JOHNSON. 

